1. Field of the Invention
The present invention relates to means for the sweeping and injection of a sample and at least one standard for use in fluid-phase chromatography apparatus.
2. Description of the Prior Art
One particular analytical technique that is used in liquid phase chromatography includes comparing the chromatogram peaks of the components of the sample with the peak of at least one pure product designated a "standard". For this purpose, it is necessary to inject at least one standard after each sample, wherein the conditions of the injections must be such that there is no overlap between peak or peaks of the sample and the peaks of the standard. Especially in liquid-phase chromatography, satisfactory conditions of injection are difficult to establish. And even though the injection of the sample and of the standard or standards by inserting a syringe through a diaphragm affords good efficiency as regards column separation, this mode of injection has its disadvantages, because, on the one hand, the conditions of injection are difficult to reproduce from injection to injection, and, on the other hand, the linear velocity of the material injected (whether sample or standard) is often higher than the linear velocity of the carrier fluid, which results in turbulence at the inlet to the separation column.
The injection of the sample and the standard or standards may also be effected by means of valves. And while the valves provide a greater reproducibility of the conditions of injection, they reduce the efficiency of the column because of their design (the presence of dead space). Thus, in the case of two valves in series, in liquid-phase chromatography, with the upstream valve providing for injection of the standard, the efficiency of the column may be reduced up to 80% with respect to the standard.